<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      /* 标签选择器一般设置一些通用样式 */
      *,
      html,
      body {
        margin: 0;
        padding: 0;
      }
      a {
        text-decoration: none;
      }
      ul,
      li {
        list-style: none;
      }
      #title {
        color: red;
      }
      /* css权重 当寻找路径越精确 权重越高 id选择器 最高 */
      .container .title {
        font-size: 30px;
        color: blue;
      }
      .title {
        color: pink;
      }

      #title:hover {
        color: blue;
        font-weight: bolder;
      }
      .btn {
        background-color: brown;
        color: white;
      }
      .btn:hover {
        font-size: 20px;
      }
      .btn:active {
        background-color: rgb(104, 148, 167);
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div>
        <span class="title">第二层级</span>
      </div>
      <span id="title" class="title">第一层级</span>
    </div>
    <ul>
      <li>123</li>
      <li>456</li>
      <li>789</li>
    </ul>
    <a href="">新浪</a>

    <span class="title">456</span>

    <span>789</span>
    <button class="btn">测试悬停和激活</button>
  </body>
</html>
